Using parallel processing for coupled BWR core kinetics and thermal hydraulics

The interactions between reactor neutron dynamics and thermal hydraulics constitute one of the most fundamental issues of boiling water reactor (BWR) safety. The interactions occur in the reactor core and can have direct effects on the integrity of fuel cladding and the cooling circuit. In unfavorable cases, such as out-of-phase power oscillations or asymmetric control rod ejection accidents, their consequences can be very severe. Several BWR neutronically coupled out-of phase oscillation incidents have been-reported. During some of the transients, both the corewide in-phase and out-of-phase power oscillations were observed. These incidents suggest a need to develop a transient three-dimensional neutronic modeling capability. The incorporation of a fully three-dimensional modeling of a reactor core into a system transient code such as TRAC allows best-estimate solution of this problem.